Vertical hall effect sensor and a brushless electric motor having a vertical hall effect sensor

ABSTRACT

A vertical Hall sensor includes a semiconductor crystal with three or more arm sections that are arranged at a uniform angle distance to each other. A central electrode and external current electrodes are arranged on the surface of the sensor, and a plurality of Hall voltage contacts is arranged therebetween. The semiconductor crystal is thick enough for a current flow to pass between the electrodes in each arm section of the semiconductor crystal, whereby the current flow produces several sensitivities in the Hall sensor corresponding to the number of arm sections with a correspondingly predefined angular dependency for a magnetic field that is directed in a parallel position with respect to the surface. The Hall voltages, which can be produced using one such multi-arm vertical Hall sensor, can be used in a reinforced and direct manner as an output signal for an electric motor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a vertical Hall effect sensor comprising asemiconductor crystal having a pair of current electrodes arranged onits surface and having a Hall effect voltage contact arranged betweenthe current electrodes, wherein the semiconductor crystal has sufficientthickness to allow a current flow between the current electrodes in thesemiconductor crystal, which current flow makes the Hall effect sensorsensitive to a magnetic field aligned parallel to the surface.

The invention also relates to a brushless electric motor having at leastone Hall effect sensor and having a permanent magnet, wherein thepermanent magnet is connected to the motor shaft such that they rotatetogether, and the Hall effect sensor is arranged opposite this permanentmagnet, and wherein the electric motor has at least three coils.

2. Description of the Prior Art

A vertical Hall effect sensor is disclosed in U.S. Pat. No. 4,987,467.Vertical hall effect sensors are integrated Hall effect sensors and havethe advantage of being sensitive to a magnetic field parallel to thechip surface. Such Hall effect sensors are used in particular foraccurate measurements of magnetic fields. A further Hall effect sensoris known from the article “A CMOS-compatible 2-D vertical Hallmagnetic-field sensor using actice [sic] carrier confinement andpost-process micromachining” by Paranjape et al. in Sensors andActuators A, Volume A53, No. 1/03, May 1996 (1996-05), pages 278 to 282,XP000620310. This is a traditional 2-D Hall effect sensor, in which twoHall effect sensors are arranged in a cruciform shape with respect toone another such that they can use a common central contact.

Known, conventional Hall effect sensors are also used for controllingelectric motors. A corresponding brushless electric motor with theassociated controller is known from the article “Effects of SoftwareSpeed-Control Algorithm on Low-Cost Six-Step Brushless DC Drives” by S.Ellerthorpe in Power Conversion-&-Intelligent Motion, Volume 22, No. 1,pages 58 to 65 (January 1996). Another brushless electric motor, whichuses three separate Hall effect sensors, is known from U.S. Pat. No.3,988,654.

In the said motor, three Hall effect sensors, which each cover 180° of acircular disk parallel to the permanent magnet, are arranged with anoffset of 120° to one another so that the voltages produced by theseHall effect sensors result in a three-bit feedback signal which definesthe rotor position with respect to six 60° areas. The informationrelating to this is used in IP, PI and PPI controllers to achieve aconstant speed from the electric motor.

These motors have the disadvantage that the corresponding systems whichcarry out the control algorithms have a space requirement that severelylimits the capabilities to miniaturize the motors. The arrangement ofthe Hall effect sensors in respect to one another is difficult withregard to the aligned planarity and with regard to the accuratealignment of the angles.

Against the background of this prior art, the invention is based on theobject of designing a vertical Hall effect sensor of the type mentionedinitially such that it allows better angular resolutions to be achieved,and in particular such that three Hall effect voltages, respectivelyshifted through 120°, can be produced when a rotating magnetic field isapplied.

A further object of the invention against the background of the saidprior art is to design an electric motor equipped with a vertical Halleffect sensor such that this electric motor can be configured as amicromotor with as small a space requirement and as simple actuation aspossible.

SUMMARY OF THE INVENTION

The first-mentioned object is achieved according to the invention for avertical Hall effect sensor of the type mentioned initially in that theHall effect sensor has three or more arm sections which are arranged atequal angular intervals from one another and which run together in acentral section, in that each arm has an outer current electrode whichis arranged opposite a central inner current electrode in the centralsection, with these current electrodes in each case forming the saidpair of current electrodes, and in that a Hall effect voltage contact isarranged between the respective outer current electrodes and the centralinner current electrode to allow a current flow between the currentelectrodes in each arm section of the semiconductor crystal, whichcurrent flow produces a number of output signals from the Hall effectsensor (for a magnetic field aligned parallel to the surface)corresponding to the number of arms and with an appropriatelypredetermined angle dependency.

Since various arms each form a complete Hall effect sensor, the Halleffect sensor can be made sensitive in a very accurate manner todifferent angles of the magnetic field in the plane of the crystalsurface. The integrated design results not only in excellent accuracywith regard to the angles of the sensors to one another due to use ofthe same crystal surface, but also in sensitivity for the samecomponents of the magnetic field.

The further object according to the invention is achieved for anelectric motor of the type mentioned initially in that the Hall effectsensor is a vertical Hall effect sensor according to the inventionhaving at least three arms, in that the number of arms corresponds tothe number of coils so that at least three Hall effect voltages whichare phase-shifted with the same phase interval between one another canbe produced by the vertical Hall effect sensor when the motor shaft isrotating, which Hall effect voltages can be supplied after amplificationto the coils as a power signal.

The use of the vertical Hall effect sensor according to the invention ina brushless electric motor allows very simple circuitry to be achievedfor this electric motor, and this is highly advantageous forminiaturization of the overall unit.

Further advantageous embodiments are characterized in the respectivedependent claims.

The invention will now be described in detail using various exemplaryembodiments of the invention and with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a known linear vertical Hall effect sensor with adevelopment in terms of the signal tapping,

FIG. 2 shows a view of a three-armed Hall effect sensor according to oneexemplary embodiment of the invention,

FIG. 3 shows a cross-sectional view through a miniaturized electricmotor having a multi-armed vertical Hall effect sensor according to theinvention and as shown in FIG. 2,

FIG. 4 shows a schematic view of a circuit diagram for driving the motorshown in FIG. 3 and having the three-armed vertical Hall effect sensorshown in FIG. 2, and

FIG. 5 shows a schematic view of a circuit diagram for driving anelectric motor which comprises five coils and has a five-armed verticalHall effect sensor according to a further exemplary embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a known vertical Hall effect sensor, whose basic principlesare described in U.S. Pat. No. 4,987,467. This document is herebyincorporated by reference in the present disclosure as a reference tothe design of such a sensor.

A semiconductor crystal 1 is the basis for the Hall effect element orthe Hall effect sensor, with this crystal 1 being cuboid, and withopposite sides thus running parallel. The reference symbols 2 and 3denote the current electrodes applied to the surface of the crystal 1. Afirst sensor contact 4 is arranged between these current electrodes,with all three contacts and electrodes being in the form of strips andrunning parallel to one another. A so-called vertical Hall effectelement, described in U.S. Pat. No. 4,987,467, then also has the part ofthe crystal 1′ shown by dashed lines and having the first inner currentelectrode 2′, the second outer current electrode 3′ and a second sensorcontact 5. Within the crystal material 1, a more conductive connection13 is formed between the current electrodes 2 and 3, and a moreconductive connection 13′ is formed between the current electrodes 2′and 3′. When a magnetic field oriented in a corresponding way to thearrow 6 is applied to this so-called vertical Hall effect sensor, thisresults in a Hall effect voltage between the two sensor electrodes 4 and5, with the various connecting levels between the contact points 4 and5, the contact points 2, 2′ and 3, 3′ and the magnetic field 6 eachrunning at right angles in this case as well. The inner currentelectrodes 2 and 2′ are integral, and form a strip.

It is now possible to dispense with the part of the vertical Hall effectsensor shown by dashed lines, and thus to operate with only one half,provided a second tapping for the Hall effect voltage is provided on therear face of the sensors.

FIG. 2 shows a view of a three-armed vertical Hall effect sensor inaccordance with the present invention, with the same features beingdenoted by the same reference symbols in each case in all the figures.The single central current electrode 2 is intended to act for all threearms 9, 29 and 49. The outer current electrodes 3, 23 and 43 arearranged facing this current electrode 2. The sensor contacts or Halleffect voltage electrodes 4, 24 and 44 are each arranged between thecentral electrode 2 and the outer electrodes 3, 23 and 43, respectively.Apart from the first layer profile of the more conductive layer 13 inthe first arm 9, the figure also shows the corresponding layer routing33 in the second arm 29.

In accordance with U.S. Pat. No. 4,987,467, this conductive layer can beprovided in a wide range of configurations and may also comprise, inparticular, the provision of a highly conductive so-called buried layerof the same conductance type as the semiconductor forming the crystal 1.

FIG. 3 now shows a view of a miniature motor which is arranged inside ahousing 50. The reference symbol 51 denotes the shaft, which is mountedin a sleeve 52. A permanent magnet 54 is arranged on a projection 53 onthe shaft 51, such that they rotate together. The permanent magnet 54 iscylindrical and has a hole. The vertical multiarmed Hall effect sensor60 is arranged facing it and at as short a distance as possible from it,and may be designed, in particular, in accordance with FIG. 2, with thecrystal surface, which is denoted by the reference symbol 61 in FIG. 2,being aligned with the permanent magnet 54.

A tubular spacer 55 is advantageously placed on the housing 52, on whichspacer 55 a printed circuit board 56 which is fitted with the sensor 60is placed and is held by the housing 50. In consequence, the magnet 54and sensor 60 can be aligned accurately parallel in a simple manner.

The circuitry of the motor shown in FIG. 3 is now illustrated in FIG. 4,which shows a fundamental circuit diagram for an electric motoraccording to the invention. The electric motor 62 has three coils, whichhave supply leads 63, 64 and 65. The reference symbol 51 once againdenotes the shaft to which the permanent magnet 60 is fitted, and thethree-armed vertical Hall effect sensor is arranged facing it, in aschematic stylized plan view illustration. The outer current electrodes3, 23 and 43 are interconnected, and are connected via an electricalpower source 66 to the inner current electrode 2. The three voltageelectrodes 4, 24 and 44 are respectively connected to first inputs ofamplifier stages 67, 68 and 69. The other inputs of the amplifiers 67,68 and 69 are each connected to voltage electrodes that follow in thecounterclockwise direction. The amplifier stages 67, 68 and 69 thus haveHall effect voltages, which are each phase-shifted through 120°, appliedto them from the three independent Hall effect sensors in the verticalHall effect sensor. These three signals 70, 71 and 72 are shownschematically in the element 73. These signals are preferablyappropriately amplified in the amplifiers 67, 68 and 69 such that theycan be passed directly to the supply leads 63, 64 and 65, so that thebrushless and preferably miniaturized electric motor 62 is drivenwithout any further electrical supply circuit. The Hall effect voltageswhich can be produced by a multiarmed vertical Hall effect sensoraccording to the invention may thus be used, after amplification, as apower signal for an electric motor.

The element 73 may be an additional external voltage source, whichproduces three phase-shifted signals 70, 71 and 72 which it provides forstarting and/or for mixing with the signals from the amplifier stages67, 68 and 69 for the electric motor 62.

Apart from the three-armed Hall effect sensor 80 shown in FIG. 4, anyother multiarmed configuration of the Hall effect sensor is likewisepossible. FIG. 5 shows a circuit diagram, corresponding to FIG. 4, of afive-armed Hall effect sensor 100. There are now five outer currentelectrodes 103, 113, 123, 133 and 143 adjoining the central currentelectrode 2. All the outer current electrodes are in turn connected tothe inner current electrode 2 via an electrical power source 66. Halleffect voltage electrodes 104, 114, 124, 134 and 144 are arrangedbetween the respective current electrode pairs 2 and 103, 113, 123, 133and 143. Analogously to FIG. 4, a number of amplifier stages, in thiscase five, 167, 168, 169, 170 and 171 are provided, corresponding to thenumber of arms. In this case as well, there are corresponding supplyleads from the five amplifiers to the five coil supplies 162, 163, 164,165 and 166 for the electric motor 62.

In each of the exemplary embodiments of a vertical Hall effect sensordescribed above, a constant current was introduced via the electrodes 2and 3, 23, 43, and the Hall effect voltage was tapped off. Thisprocedure always leads to phase-shifted output signals, which oscillateabout 0 volts and thus essentially have no DC voltage components. Incontrast, when the described Hall effect sensors are operated at aconstant voltage, and thus with a variable current, the output voltageoscillates about a value other than 0, for example 3 volts, that is tosay with a DC voltage component.

Apart from the illustrated capability to form differences in theamplifier stages 67 and 167 et seq., each output signal from the Halleffect voltage contacts can also be amplified and supplied to the motor62 individually. This situation, which is not shown in the drawings,leads to a shift in the Hall effect voltages for different magneticfield strengths, that is to say the output voltages at the “zerocrossings” of the three-armed sensors at 0 and 180, 60 and 240, or 120and 300 degrees are not the same, for different magnetic fieldstrengths.

The Hall effect sensor according to the invention can be used for otherapplications, in addition to the described use for driving micromotors,in all those areas in which Hall effect sensors operating in variousorientations are required in a confined space. Apart from theillustrated three-armed and five-armed vertical Hall effect sensors, anyother number of sensor arms greater than three is also possible.

The sensor per se has the advantage that it is an integrated sensorwhich does not cause any problems whatsoever in its production withregard to the parallel and in this case flush alignment of the planes ofthe contact surfaces, in this case in the surface 61. The alignment andsize of the contact surfaces themselves can also be predetermined veryaccurately. As a result of the integration process, the angle of 120°between adjacent arms for the three-armed sensor as shown in FIG. 2, andthe angle of 72° between adjacent arms for the five-armed sensor whichis shown in FIG. 5 can be produced with very high accuracy.

If the Hall effect sensor has an even number of arms, for example six,mutually opposite Hall effect sensor arms are interconnected to form acomplete vertical Hall effect sensor as shown in FIG. 1, in addition tothe Hall effect voltage sensitivities, of which there are six at phaseintervals of 60 degrees in this case, in the manner described inconjunction with the figures. The example with six arms chosen in thissection then results in three Hall effect voltage sensitivities at phaseintervals of 120 degrees to one another, as in the three-armed Halleffect sensor shown in FIG. 2. However, the circuit complexity isconsiderably greater. The advantage of the solution shown in FIGS. 2 and3 is, in particular, also the fact that considerably fewer contacts arerequired, and the circuitry of the sensor can be simpler.

What is claimed is:
 1. A vertical Hall effect sensor, comprising: asemiconductor crystal having a pair of current electrodes arranged on asurface thereof and having a Hall effect voltage contact arrangedbetween the pair of current electrodes, wherein the semiconductorcrystal has sufficient thickness to allow a current flow between thepair of current electrodes in the semiconductor crystal, which currentflow makes the Hall effect sensor sensitive to a magnetic field alignedparallel to the surface, wherein the Hall effect sensor has at leastthree arm sections which are arranged at equal angular intervals fromone another and which run together in a central section, wherein each ofthe arm sections has an outer current electrode which is arrangedopposite a central inner current electrode in the central section, withthe outer current electrodes in each case forming the pair of currentelectrodes, wherein a Hall effect voltage contact is arranged betweenthe respective outer current electrodes and the central inner currentelectrodes to allow a current flow between the outer current electrodesin each of the arm sections of the semiconductor crystal, which currentflow produces a plurality of output signals from the Hall effect sensorfor a magnetic field aligned parallel to the surface corresponding tothe number of arm sections and with a predetermined angle dependency,and wherein the three arm sections are arranged at an angle of 120° toone another.
 2. The vertical Hall effect sensor as claimed in claim 1,wherein a buried layer is provided in each of the arm sections of thesemiconductor crystal for producing the current flow.
 3. The verticalHall effect sensor as claimed in claim 1, wherein the outer currentelectrodes are electrically conductive strips, and wherein the Halleffect voltage contacts are electrically conductive strips arrangedparallel to the outer current electrodes.
 4. The vertical Hall effectsensor as claimed in claim 1, wherein a buried layer is provided in eachof the arm sections of the semiconductor crystal for producing thecurrent flow.
 5. The vertical Hall effect sensor as claimed in claim 1,wherein the outer current electrodes are electrically conductive strips,and wherein the Hall effect voltage contacts are electrically conductivestrips arranged parallel to the outer current electrodes.
 6. Thevertical Hall effect sensor as claimed in claim 2, wherein the outercurrent electrodes are electrically conductive strips, and wherein theHall effect voltage contacts are electrically conductive strips arrangedparallel to the outer current electrodes.
 7. A vertical Hall effectsensor, comprising: a semiconductor crystal having a pair of currentelectrodes arranged on a surface thereof and having a Hall effectvoltage contact arranged between the pair of current electrodes, whereinthe semiconductor crystal has sufficient thickness to allow a currentflow between the pair of current electrodes in the semiconductorcrystal, which current flow makes the Hall effect sensor sensitive to amagnetic field aligned parallel to the surface, wherein the Hall effectsensor has at least five arm sections which are arranged at equalangular intervals from one another and which run together in a centralsection, wherein each of the arm sections has an outer current electrodewhich is arranged opposite a central inner current electrode in thecentral section, with the outer current electrodes in each case formingthe pair of current electrodes, wherein a Hall effect voltage contact isarranged between the respective outer current electrodes and the centralinner current electrodes to allow a current flow between the outercurrent electrodes in each of the arm sections of the semiconductorcrystal, which current flow produces a plurality of output signals fromthe Hall effect sensor for a magnetic field aligned parallel to thesurface corresponding to the number of arm sections and with apredetermined angle dependency, and wherein the five arm sections arearranged at an angle of 72° to one another.